In the art, a problem arises when an electric system comprises one or more components which require a higher supply voltage to operate adequately than a power supply of the electric system is capable of delivering.
U.S. Pat. No. 7,911,758 discloses a solenoid control circuit including a power source in series with a sensing element, an inductor to actuate a valve, an energy storage device to store and discharge energy into the inductor, diodes to control current flow, and switches and a controller to control the circuit. The circuit may be operated by closing a first switch, thereby allowing a source current to flow through an inductor; opening the first switch, thereby forcing a charge current to flow through an energy storage device utilizing the inductance of the inductor; repeating these steps until the energy storage device is sufficiently charged; and upon command, closing a second switch, thereby forcing a discharge current to flow from the energy storage device to the inductor causing the inductor to produce an actuating magnetic field thereby actuating a mechanical valve.
However, in order to determine whether the energy storage device has been sufficiently charged, either the charging cycles are repeated a predetermined number of times as determined during manufacturing, or a microcontroller monitors the above mentioned sensing element. Repeating the charging cycles a predetermined number of times has the disadvantage on the one hand that there is a risk that the energy storage device is charged more than necessary, which is undesirable from a power consumption perspective, or on the other that the energy storage device is not sufficiently charged, which will prevent the solenoid from operating correctly. A disadvantage with the approach of having a microcontroller measuring the sensing device to determine whether the energy storage device is sufficiently charged is that a separate sensing device in the form of e.g. a precision shunt resistor is used to measure current passing through the sensing device.